Propylene glycol (PG) is a synthetic liquid substance used extensively across many industries, leading to questions about its safety for expectant mothers. Its widespread use in consumer products means exposure during pregnancy is nearly constant. While PG is generally considered non-toxic, the unique physiological changes of pregnancy can alter how the body processes substances.
Understanding Propylene Glycol
Propylene glycol is a clear, colorless, and nearly odorless liquid used in commercial products. It is primarily valued as a solvent, dissolving many substances that water cannot. This makes it an excellent carrier for flavorings and colors in food and pharmaceutical products. PG also acts as a humectant, helping products retain moisture, which contributes to the texture of baked goods and the hydrating effect of cosmetics.
The low toxicity and cost-effectiveness of PG contribute to its ubiquity. It is important to distinguish between the grades of this substance. The food and pharmaceutical industries use a high-purity form designated as USP/EP (United States Pharmacopoeia/European Pharmacopoeia) grade, which meets strict quality standards. Industrial-grade PG is used in applications like de-icing solutions and antifreeze, but the USP/EP grade is approved for human consumption and topical use.
Common Routes of Exposure During Pregnancy
Expectant mothers encounter propylene glycol through three main routes: ingestion, topical application, and inhalation. Ingestion is the most common pathway, as PG is used as a solvent and stabilizer in many processed foods, soft drinks, and flavor concentrates. It may be listed on ingredient labels as propylene glycol, E1520, or as a component of “natural flavors.”
The dermal route of exposure is frequent due to its inclusion in personal care products. PG is found in cosmetics, lotions, deodorants, shampoos, and topical medications where it functions as a humectant and carrier. Although the skin is generally a poor absorber of PG, this exposure route is continuous.
Inhalation represents a pathway for potentially higher absorption, particularly with the use of electronic cigarettes. PG is a primary component of the e-liquid base, and when heated, it creates the visible aerosol that is inhaled. Other sources of inhalation exposure include theatrical fog or mist used in entertainment venues or for fire safety training.
Scientific Assessment of Prenatal Safety
The safety of propylene glycol has been extensively studied. The U.S. Food and Drug Administration (FDA) classifies it as “Generally Recognized As Safe” (GRAS) for use as a direct food additive. This classification applies to non-pregnant adults under typical low exposure levels and for ingestion, not necessarily for all routes or high-dose scenarios. Dedicated human pregnancy studies are absent due to ethical limitations, so the current assessment relies heavily on animal data and toxicological principles.
High-dose animal studies, designed to push the limits of toxicity, show that PG does not cause adverse developmental or reproductive effects in several species, including mice, rats, and rabbits. This is true even at doses far exceeding typical human exposure. For example, pregnant mice showed no adverse developmental effects after receiving extremely high oral doses of approximately 10,000 mg/kg per day. These findings suggest the chemical does not act as a developmental toxicant under normal exposure conditions.
A theoretical concern arises from the metabolism of PG, which is broken down in the liver into lactic acid and pyruvic acid. In cases of high, acute exposure—often from large-volume intravenous medications—this rapid metabolism can overwhelm the body’s clearance mechanisms. This leads to an increase in lactic acid and a metabolic acidosis. Since pregnant women have altered physiology, and the fetus relies on the mother for clearance, a significant acute PG overdose is considered a theoretical risk. However, this is rare outside of medical emergencies. The average estimated daily intake of PG through food is well below the level associated with metabolic concerns.
Recommendations for Minimizing Exposure
Given the scientific consensus, a pregnant person does not need to eliminate all products containing PG, but precautionary steps can minimize higher-risk exposures. The most significant recommendation is the strict avoidance of vaping and e-cigarette use. Inhalation delivers a much higher, concentrated dose of PG than ingestion or topical use. The lack of comprehensive inhalation safety data for this population warrants caution regarding all inhaled sources.
For oral exposure, minimizing the consumption of heavily processed foods, packaged snacks, and highly flavored beverages will reduce dietary intake of PG. Choosing whole, less-manufactured foods is a simple way to decrease exposure to this and other common food additives. If a physician prescribes an oral or intravenous medication that lists PG as a diluent or excipient, the patient should discuss the dose and necessity with their healthcare provider.
Low-level exposure from cosmetics and personal care products is considered negligible. However, switching to PG-free alternatives is an easy precautionary measure for concerned individuals. Reducing continuous, high-volume sources of exposure is the most practical strategy, as the small amounts found in most foods and topical products are considered safe.